The present invention relates to an air-fuel ratio control apparatus for internal combustion engines.
Air-fuel ratio control apparatus are known in the art in which when a vehicle decelerates from its steady-state condition and comes to a stop, that is, when the engine is placed in its idle mode of operation, the air-fuel ratio control is switched to an open loop control so that the air-fuel ratio correction amount is held at the average value of the air-fuel ratio correction amount during the starting period of the engine idling operation and the air-fuel ratio control is stopped. Thus there is a disadvantage that if, in this condition, the vehicle accelerates from its reset condition and comes into a steady-state operation, the air-fuel ratio correction amount is reduced thus deteriorating the acceleration performance and increasing the amount of NOx in the exhaust gas.